J. AbrahamM. AgliettaC. AguirreD. AllardI. AllekotteP. AllisonC. ÁlvarezJaime Álvarez-MuñizM. AmbrosioLuis A. Anchordoqui2026-03-222026-03-22200710.1016/j.astropartphys.2006.10.004https://doi.org/10.1016/j.astropartphys.2006.10.004https://andeanlibrary.org/handle/123456789/44113Citaciones: 120enPierre Auger ObservatoryPhysicsAugerCosmic rayPhotonAstrophysicsObservatoryUltra-high-energy cosmic rayEvent (particle physics)DetectorAn upper limit to the photon fraction in cosmic rays above 1019eV from the Pierre Auger Observatoryarticle